SMA and ALMA Studies of Disk- and Planet Formation around Low-mass Protostars

TL;DR

This study uses SMA and ALMA observations to reveal that disk and planet formation around low-mass protostars occurs early, with Keplerian disks present in Class 0 and I sources and signs of planet formation in disks.

Contribution

It provides new high-resolution ALMA data showing the presence of Keplerian disks in early protostellar stages and evidence of planet formation during the protostellar phase.

Findings

Keplerian disks are common around Class I sources.

Disks in some Class 0 sources are smaller or undetectable.

Gaps in HL Tau's disk suggest early planet formation.

Abstract

We report our current SMA and ALMA studies of disk and planet formation around protostars. We have revealed that $r \gtrsim$100 AU scale disks in Keplerian rotation are ubiquitous around Class I sources. These Class I Keplerian disks are often embedded in rotating and infalling protostellar envelopes. The infalling speeds of the protostellar envelopes are typically $\sim$ 3-times smaller than the free-fall velocities, and the rotational profiles follow the $r^{-1}$ profile, that is, rotation with the conserved specific angular momentum. Our latest high-resolution ($\sim$0$\farcs$5) ALMA studies, as well as the other studies in the literature, have unveiled that $r \sim$100-AU scale Keplerian disks are also present in several Class 0 protostars, while in the other Class 0 sources the inferred upper limits of the Keplerian disks are very small ($r \lessim$20 AU). Our recent data analyses of the ALMA long baseline data of the Class I-II source HL Tau have revealed gaps in molecular gas as well as in dust in the surrounding disk, suggesting the presence of sub-Jovian planets in the disk. These results imply that disk and planet formation should be completed in the protostellar stage.